* Basic hub functions:
    * Write-ready, ready ready
    * EAGAIN behavior with mocks
    * Socket close
    * Timers and callbacks

* Client:

* Util
    * Pool, client failure, release vs. reclaim
    * Queue, callback patterns, iterator, locks etc

* Core
    * bytes(), until() behavior and combinations
    * @call into
    * defer to thread behavior
    * connections vs. loops
    * loops not using connection-specific things
    * run tests over tls too--both client and server
